Shock absorber

ABSTRACT

The invention provides a hydraulic shock absorber for controlling an attenuating force in a very low speed range and a medium or high speed range of the speed of a piston. A leaf valve for the high speed range and another leaf valve for the medium or high speed range are disposed for opening and closing movement at an exit end of a port formed in a partition wall member such as the piston. The leaf valve for the low speed range is supported at a rear face of an inner peripheral portion thereof for up and down floating movement on an upper face of a valve stopper. In the medium or high speed range, the leaf valve for the low speed range is deflected to move the inner peripheral portion thereof floatingly, which prevents the leaf valve from being deflected excessively and hence prevents a possible break of the leaf valve.

This is a continuation of application Ser. No. 07/966,719 filed Oct. 26,1992 now abandoned, which is a divisional of application Ser. No.07/857,710 filed on Mar. 25, 1992 now U.S. Pat. No. 5,332,069, which isa continuation of Ser. No. 07/575,201 filed Aug. 30, 1990 abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a hydraulic shock absorber suitable for use incontrol of the attenuating force of a piston in a medium or high speedrange of the speed of the piston and also in control of the attenuatingforce of the piston in a very low speed range of the speed of thepiston.

2. Description of the Prior Art

In recent years, there is a tendency that a hydraulic shock absorber isformed such that, in order to improve, for example, the drivability andthe stability in driving of a vehicle, it may perform not only controlof attenuating force of a piston in a medium or high speed range of thespeed of the piston but also control of the piston in a very low speedrange of the speed of the piston.

An exemplary one of conventional hydraulic shock absorbers is disclosed,for example, in Japanese Utility Model Laid-Open No. 60-101242. Theconventional hydraulic shock absorber is shown in FIG. 11. Referring toFIG. 11, the conventional hydraulic shock absorber includes a cylinder1, a piston member 2 disposed in the cylinder 1 to define an upper orfirst oil chamber A and a lower or second oil chamber B in the cylinder1 and constructed to communicate the oil chambers A and B with eachother, and an expansion side attenuating valve 3 mounted on the pistonmember 2.

The attenuating valve 3 includes a leaf valve 3adisposed on the upstreamside for generating the attenuating force in the very low speed range ofthe speed of the piston, and another leaf valve 3b disposed on thedownstream side for generating an attenuating force in the medium orhigh speed range of the speed of the piston. Each of the leaf valves 3aand 3b is secured at an inner peripheral portion thereof and constructedto be deflected at an outer peripheral portion thereof to generate apredetermined attenuating force.

The leaf valve 3a is disposed such that it closes an opening at a lowerend of an inner port 20a perforated in a piston body 20 which constitutethe piston member 2 while the other leaf valve 3b is disposed such thatit covers over the leaf valve 3a from below. A spring sheet 4 isdisposed on a back or lower face of the leaf valve 3a, and it isnormally acted upon by urging force of a spring 5 from below.

With the hydraulic shock absorber, when the piston member 2 is making anexpanding movement in which it moves up in the cylinder 1 and the pistonspeed is in the very low speed range, an outer peripheral portion of theleaf valve 3a is deflected by a flow of hydraulic operating fluid fromthe upper oil chamber A which serves as a higher pressure side oilchamber, whereupon a predetermined attenuating force is generated. Onthe other hand, in the medium or high speed range of the piston speed,an outer peripheral portion of the leaf valve 3b is deflected, inaddition to such deflection of the leaf valve 3a as described above, bya flow of hydraulic operating fluid from the oil chamber A to push downthe spring sheet 4 overcoming the urging force of the spring 5,whereupon a predetermined attenuating force is generated.

Incidentally, the piston member 2 of the conventional hydraulic shockabsorber is constructed such that hydraulic operating fluid comingaround an outer peripheral portion of the leaf valve 3a is introducedinto an outer port 20b perforated at a location of the piston body 20radially outwardly of the inner port 20a by way of a sub port 20c.

The conventional hydraulic shock absorber. however, is disadvantageousin that the life of the leaf valve 3a is short.

In particular, the conventional hydraulic shock absorber carries outhigh attenuating force control when the leaf valve 3b is deflected.Thereupon, however, an outer peripheral portion of the leaf valve 3a isdeflected simultaneously over a greater extent, and accordingly, theleaf valve 3a is deflected every time an attenuating force is generatedby the hydraulic shock absorber. Since the leaf valve 3a is secured atan inner peripheral portion thereof, it is likely to be damaged ofbroken due to such repetitive deflections, which will decrease the lifeof the leaf valve 3a.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a hydraulic shockabsorber wherein the life of a leaf valve for the control of theattenuating force in a very low speed range of the speed of a piston isimproved and such control of the attenuating force in the very low speedrange of the piston speed is facilitated.

It is another object of the present invention to provide a hydraulicshock absorber wherein controls of the attenuating force in a very lowspeed range and in a medium or high speed range of the speed of a pistoncan be performed independently of each other.

It is a further object of the present invention to provide a hydraulicshock absorber wherein a leaf valve is superior in durability and canexpand the degree of freedom in the attenuating force characteristic ina very low speed range of the speed of a piston.

In order to attain the objects according to the present invention, thereis provided a hydraulic shock absorber, comprising a cylinder, apartition wall member disposed in the cylinder to define a pair of oilchambers in the cylinder, the oil chambers being in communication witheach other by way of a port formed in the partition wall member, anattenuating valve located at an exit end of the port for opening andclosing movement, the attenuating valve including a leaf valve for a lowspeed range and another leaf valve for a medium or high speed rangedisposed in a suitable spaced relationship on the rear face side of theleaf valve for the low speed range, and a valve stopper for supporting,on an upper face thereof, a rear face of an inner peripheral portion ofthe leaf valve for the low speed range for up and down floatingmovement.

With the hydraulic shock absorber, when the hydraulic shock absorber ismaking an expanding movement and the speed of the piston is in a verylow speed range, hydraulic operating fluid from one of the oil chambersin the cylinder remote from the exit end of the port deflects an outerperipheral portion of the leaf valve for the low speed range, whereuponpredetermined attenuating force is generated by such deflection of theouter peripheral portion of the leaf valve for the low speed range.

In this instance, the inner peripheral portion of the leaf valve for thelow speed range is supported in a fixed condition on the valve stopper.

On the other hand, when the hydraulic shock absorber is making anexpanding movement and the piston speed is in the medium or high speedrange, hydraulic operating fluid from the one oil chamber in thecylinder deflects the outer peripheral portion of the leaf valve for thelow speed range, which then deflects an outer peripheral portion of theleaf valve for the medium or high speed range so that it flows out intothe other oil chamber, whereupon another high predetermined attenuatingforce is generated by such deflection of the outer peripheral portion ofthe leaf valve for the medium or high speed range.

When the outer peripheral portion of the leaf valve for the medium orhigh speed range is deflected, the inner peripheral portion of the leafvalve for the low speed range is supported in a floating condition onthe valve stopper. Consequently, the leaf valve for the low speed rangeis prevented from being deflected excessively.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings inwhich like parts are denoted by like reference characters all throughthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial vertical sectional front elevational view of ahydraulic shock absorber showing an embodiment of the present invention:

FIGS. 2(A), 2(B) and 2(C) are partial plan views of different leafvalves of an attenuating valve of the hydraulic shock absorber of FIG.1, and FIG. 2(D) is a plan view of a valve stopper of the hydraulicshock absorber of FIG. 1;

FIGS. 3 to 6 are enlarged partial vertical sectional front elevationalviews showing different attenuating valves for use with the hydraulicshock absorber of FIG. 1;

FIG. 7 is a partial vertical sectional front elevational view of anotherhydraulic shock absorber showing another embodiment of the presentinvention;

FIGS. 8, 9 and 10 are enlarged vertical sectional front elevationalviews of different attenuating valves for use with the hydraulic shockabsorber of FIG. 7; and

FIG. 11 is a partial vertical sectional front elevational view of aconventional hydraulic shock absorber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown a hydraulic shock absorber towhich the present invention is applied. The hydraulic shock absorbershown includes a cylinder 1, a piston rod 6 fitted for movement into andout of the cylinder 1, and a piston member 2 serving as a partition wallmember mounted at an end of the piston rod 6.

The piston member 2 includes a piston body 20 disposed in the cylinder 1to define two oil chambers including an upper oil chamber A and a loweroil chamber B in the cylinder 1 and has a pair of ports 20d and 20eperforated therein so as to communicate the oil chambers A and B witheach other when the piston member 2 is slidably moved in the cylinder 1upon movement of the piston rod 6 into and out of the cylinder 1.

The piston member 2 further includes an expansion side attenuating valve3 mounted on the piston body 20 thereof adjacent an exit opening at alower end of the port 20d while a compression side attenuating valve 7is mounted on the piston body 20 adjacent an exit opening at an upperend of the other port 20e.

The piston rod 6 has a faucet portion 6a extending from a shaft portion6c into the cylinder 2 with a stepped portion 6d formed therebetween. Athreaded portion 6b is formed at a lower end portion of the faucetportion 6a of the piston rod 6, and a piston nut 60 is screwed on thethreaded portion 6b. A stopper 21 is disposed on the piston nut 60 andfitted around the faucet portion 6a of the piston rod 6. Another stopper22 is disposed just below the stepped portion 6d of the piston rod 6 andfitted around the faucet portion 6a of the piston rod 6. The expansionside attenuating valve 3 and the compression side attenuating valve 7are held at inner peripheral portions thereof between an upper end faceof the stopper 21 and a lower end face the other stopper 22 by way of apair of annular seats 23 and 24, respectively, with the piston body 20held therebetween.

The expansion side attenuating valve 3 utilizes the piston body 20 as avalve seat member thereof and is disposed at a lower end in FIG. 1 ofthe piston body 20 such that it is opposed to an annular groove 20fwhich is formed at the lower end of the piston body 20 in a contiguousrelationship to an opening at a lower end of the port 20d formed in thepiston body 20. The expansion side attenuating valve 3 includes a leafvalve 30 for a low speed range, a plurality of leaf valves 31 for amedium or high speed range and a recessed leaf valve 32 and isconstructed such that it generates predetermined attenuating force bydeflection of an outer peripheral portion of the leaf valve 30 when thepiston speed is in a very low speed range, but it generates, when thepiston speed is in a medium or high speed range, another predeterminedattenuating force by deflection of outer peripheral portions of the leafvalves 31 and the recessed leaf valve 32.

The leaf valve 30 has a body portion 30a formed as an annular narrowring as shown in FIG. 2(A) and disposed fixedly on inner and outerannular valve seat portions 20g and 20h which are formed on the pistonbody 20 such that they are stepped with respect to the annular groove20f.

The leaf valves 31 are disposed in layers and each has a body portion31a formed as an annular wide ring as shown in FIG. 2(B). The leafvalves 31 are held at inner peripheral portions thereof between theannular seat 23 and an inner periphery fixing portion 20i of the pistonbody 20 with the recessed leaf valve 32 interposed between the leafvalves 31 and the inner periphery fixing portion 20i of the piston body20.

The leaf valves 31 are disposed such that outer peripheral portionsthereof are opposed to an annular valve seat portion 20j formed at alocation of the piston body 20 radially outwardly of the annular groove20f to define the annular groove 20f.

The recessed leaf valve 32 has, as shown in FIG. 2(C), a body portion32a formed as a wide annular ring and has a plurality of recessed holes32b formed in a suitable circumferentially spaced relationship along anouter periphery of the body portion 32a thereof.

The recessed leaf valve 32 lies on a pressure receiving face, that is, atop face of the leaf valves 31. Thus, the recessed leaf valve 32 isfixedly held at an inner peripheral portion thereof together with innerperipheral portions of the leaf valves 31 while it contacts at an outerperipheral portion thereof with the annular valve seat portion 20j ofthe piston body 20.

A valve stopper 33 having suitable spring force and serving as an urgingmember is interposed between the leaf valve 30 and the recessed leafvalve 32, and the leaf valve 30 is supported on an upper face of thevalve stopper 33 such that it may be floatingly movable at an innerperipheral portion thereof.

In particular, the valve stopper 33 has a body portion 33a formed as anarrow annular ring as shown in FIG. 2(D) and has a curved cross sectionas taken in a radial direction such that it may generally have the formof an initially coned disk spring of a leaf spring.

The valve stopper 33 is disposed such that an inner peripheral surfacethereof contacts with a lower face of an inner peripheral portion of theleaf valve 30 while an outer peripheral portion thereof contacts with apressure receiving face of the recessed leaf valve 32 on the pressurereceiving face side of the leaf valves 31.

Consequently, the leaf valve 30 resiliently supported on the valvestopper 33, is not restricted from movement at an outer peripheralportion thereof. Accordingly, when the hydraulic pressure acting on apressure receiving face of the leaf valve 30 is low, the leaf valve 30is deflected only at an outer peripheral portion thereof, but when thehydraulic pressure is high, the inner peripheral portion of the leafvalve 30 is moved down by hydraulic operating fluid overcoming thespring force of the valve stopper 33.

In short, the leaf valve 30 is supported such that, when the hydraulicpressure acting on the pressure receiving face thereof is high, that is,when the piston speed is in the medium or high speed range, the innerperipheral portion thereof is moved down in response to the hydraulicpressure.

The compression side attenuating valve 7 is composed of a plurality ofannular leaf valves 70 layered one on another and is disposed on theother or upper end in FIG. 1 of the piston body 20 such that the pistonbody 20 may act as a valve seat member therefor.

In particular, the compression side attenuating valve 70 is held at aninner peripheral portion thereof between the stopper 22 and an innerperiphery fixing portion 20k of the piston body 20 with the annular seat24 interposed between the stopper 22 and the compression sideattenuating valve 7. The compression side attenuating valve 70 isdisposed such that an outer peripheral portion thereof is opposed to anannular groove 201 formed on the piston body 20 in a contiguousrelationship to an opening at an upper end of the port 20e.

With the hydraulic shock absorber having such construction as describedabove, when the piston rod 6 moves into and out of the cylinder 1, thehydraulic shock absorber makes expanding and compressing movement,whereupon the piston member 2 is slidably moved in the cylinder 2.

Then, when the piston member 2 is slidably moved in the cylinder 1, theupper oil chamber A and the lower oil chamber B in the cylinder 2 arecommunicated with each other by way of the piston member 2. Particularlyupon expanding movement of the hydraulic shock absorber, a predeterminedexpansion side attenuating force is generated by way of hydraulicoperating fluid which passes through the attenuating valve 3 disposed onthe piston member 2.

In particular, when the hydraulic shock absorber is making an expandingoperation and the piston speed is in the very low speed range, hydraulicoperating fluid from the upper oil chamber A in the cylinder 1 comesaround an outer periphery of the leaf valve 30 to the pressure receivingface of the recessed leaf valve 32 and then flows out into the lower oilchamber B in the cylinder 1 by way of the recessed holes 32a on theouter periphery of the recessed leaf valve 32.

Thereupon, since the leaf valve 30 of the attenuating valve 3 isdeflected only at the outer peripheral portion thereof while the innerperipheral portion thereof is supported in a fixed condition under thespring force of the valve stopper 33, predetermined attenuating force isgenerated upon deflection of such outer peripheral portion of the leafvalve 30.

On the other hand, when the hydraulic shock absorber is making anexpanding movement and the piston speed is in the medium or high spedrange, the inner peripheral portion of the leaf valve 30 is moved downby a hydraulic pressure of hydraulic operating fluid from the upper oilchamber A in the cylinder 1 overcoming the spring force of the valvestopper 33. Consequently, a greater valve opening is obtained at theouter peripheral portion side of the leaf valve 30.

Accordingly, in the medium or high speed range of the piston speed,hydraulic operating fluid from the upper oil chamber A in the cylinder 1flows out around the outer periphery of the leaf valve 30 thus opened toa great extent to the pressure receiving face of the valves 31 below andthen flows out into the lower oil chamber B while deflecting outerperipheral portions of the valves 31 together with an outer peripheralportion of the recessed leaf valve 32.

Thereupon, a predetermined attenuating force is generated by suchdefection of the outer peripheral portions of the leaf valves 31 and therecessed leaf valve 32 disposed adjacent the leaf valves 31.

Thus, the leaf valve 30 is supported in a floating condition at theinner peripheral portion thereof when the outer peripheral portions ofthe leaf valves 31 and recessed leaf valve 32 are defected, that is,when the piston speed exceeds an effective operation range. Accordingly,the leaf valve 30 operates only so as to increase its valve opening forthe leaf valves 31 on the downstream side, and consequently, a highdeflection lead does not act upon the inner peripheral portion of theleaf valve 30, which will prevent possible trouble with regard to leafvalve 30, such as a break.

Accordingly, with the hydraulic shock absorber of the embodimentdescribed above, it is possible to freely set characteristics of theleaf valve 30 such as rigidity separately from characteristics of theleaf valves 31 and recessed leaf valve 32 such as rigidity or aquantity, and accordingly, not only control of the attenuating force inthe medium or high speed range of the piston speed but also control ofthe attenuating force in the very low speed range of the piston speedcan be performed with certainty.

FIGS. 3 to 6 show different forms of the attenuating valve 3 describedabove. The attenuating valves of FIGS. 3 to 6 have somewhat commonconstructions to that of the attenuating valve 3 shown in FIGS. 1 to2(D), and like parts are denoted by like reference numerals andoverlapping description thereof is omitted herein to avoid redundancy.

Referring first to FIG. 3, the attenuating valve 3 shown includes astopper member 34 interposed between a valve stopper 33 and a recessedleaf valve 32. The valve stopper 33 is supported at an outer peripherallower end thereof on the stopper member 34.

A load which acts upon the leaf valve 30 in a medium or high speed rangeof the piston speed does not at all act upon the recessed leaf valve 32and hence upon leaf valves 31 by way of the valve stopper 33.Accordingly, it is an advantage that such a load need not be taken intoconsideration in setting of the leaf valves 31.

It is to be noted that, in the attenuating valve 3 of FIG. 3, an annularseat 35 is interposed between an inner peripheral portion of the stoppermember 34 and an inner peripheral portion of the recessed leaf valve 32.

Referring now to FIG. 4, the attenuating valve 3 shown includes a leafvalve 30 received at inner and outer peripheral portions thereof onvalve seat portions 20g and 20h formed on radially inner and outerperipheral portions of an end face of a piston body 20. The inner sidevalve seat portion 20g is formed in level with a fixing portion 20iwhich is formed on a radially inward portion of the end face of thepiston body 20.

An annular seat 36 is disposed on the fixing portion 20i of the pistonbody 20 radially inwardly of the leaf valve 30 and a valve stopper 33and is formed so as to have such a thickness as will allow deformationof the valve stopper 33 to provide upward and downward floating movementof the leaf valve 30.

Accordingly, with the attenuating valve 3 of FIG. 4, machining operationof the lower end face of the piston body 20 is easy comparing with thatof the attenuating valve 30 shown in FIG. 1.

Referring now to FIG. 5, the attenuating valve 3 shown includes a leafvalve 30 which is disposed in a non-restricted condition.

In particular, the leaf valve 30 is normally received at an outerperipheral portion thereof on a valve seat 20h formed on a piston body20 while an inner peripheral portion thereof is set in a floatingcondition without being received on a valve seat 20g formed at aradially inner portion of the piston body 20.

An annular seat 36 having the same thickness as the leaf valve 30 isdisposed in the inside of the leaf valve 30 and received on the valveseat 20g of the piston body 20, and a valve stopper 37 having a curvedcross section is mounted on a lower face of the annular seat 36 adjacenta lower face of the leaf valve 30.

Also in the attenuating valve 3 of FIG. 5, an annular seat 35 isinterposed between an inner peripheral portion of the valve stopper 37and an inner peripheral portion of a recessed leaf valve 32 below.

Accordingly, with the attenuating valve 3 of FIG. 5, even if an outerperipheral portion of the leaf valve 30 is deflected to a great extentin the medium or high speed range of the piston speed in which outerperipheral portions of leaf springs 31 are deflected to a great extent,the leaf valve 30 will make a movement like a lever to move the innerperipheral portion thereof into an annular groove 20f formed in thepiston body 20. Consequently, a great bending phenomenon does not takeplace at the inner peripheral portion of the leaf valve 30.

Referring now to FIG. 6, the attenuating valve 3 shown includes a leafvalve 30 which is disposed in a non-restricted condition similarly as inthe attenuating valve 3 of FIG. 5. A valve stopper 37' is disposed on aninner peripheral portion of a lower face of the leaf valve 30, and aguiding annular seat 37' is disposed radially inwardly of the leaf valve30 and valve stopper 37.

Consequently, the leaf valve 30 is supported on the valve stopper 37below, and when an outer peripheral portion of the leaf valve 30 isdeflected to a great extent in the medium or high speed range of thepiston speed in which outer peripheral portions of leaf valves 31 aredeflected to a great extent, the leaf valve 30 is supported at an outerperipheral portion of the valve stopper 37.

Accordingly, also with the attenuating valve 3 of FIG. 6, the leaf valve30 makes a movement like a lever to move an inner peripheral portionthereof into an annular groove 20f formed in a piston body 20, andconsequently, a great bending phenomenon does not take place at theinner peripheral portion of the leaf valve 30.

While the hydraulic shock absorber described above is constructed suchthat the attenuating valve 3 is disposed in the piston member 2 in thecylinder 1, similar effects can be attained otherwise if the attenuatingvalve 3 is disposed at a base valve section (not shown) at a lower endin the inside of the cylinder 1 or at an attenuating force generatingsection (not shown) installed in a separate tank outside the cylinder 1or at some other section.

Referring now to FIG. 7, there is shown another hydraulic shock absorberto which the present invention is applied. The shock absorber shownincludes a cylinder 1, and a piston body 20' secured to an end of apiston rod 6 by means of a nut 60 and disposed for sliding movement inthe cylinder 1. Hydraulic operating fluid is provided in oil chambers Aand B defined by the piston body 20' in the cylinder 1.

The piston body 20' has a pair of passages 46 and 47 perforated thereinso as to communicate the oil chambers A and B with each other. Anon-return valve 49 is normally held in resilient contact with a valveseat face 48 around the passage 46 on the oil chamber A side under theurging force of a spring 62 while a leaf valve mechanism 50 which servesas an attenuating valve for generating an expansion side attenuatingforce is disposed on a valve seat face 61 around the other passage 47 onthe oil chamber B side.

Referring to FIG. 8, the leaf valve mechanism 50 includes a leaf valve51 for a lower speed range having an outer peripheral portion of a facethereof held in contact with the seat face 61 and having an innerperipheral portion of the other face thereof spaced away from an innerperipheral seat face 52 and held in contact with a spacer 53 serving asa valve stopper, and a multiple leaf valve 54 for a medium or high speedrange having the same diameter as the leaf valve 51. The leaf valve 51and the multiple leaf valve 54 are disposed in vertical planes in anoverlapping relationship in a perpendicular direction with the spacer 53interposed therebetween, and the leaf valve 51 is supported at theradially inward end side thereof for up and down floating movement onthe spacer 53 while the other leaf valve 54 is secured at an innerperipheral portion thereof such that the leaf valves 51 and 54 functionusing the valve seat face 61 as a common valve controlling acting face.An annular float valve 55 having a thickness smaller than that of thespacer 53 is secured to the leaf valve 54 and located in a gap betweenthe leaf valves 51 and 54.

Consequently, a gap d smaller than the thickness of the spacer 53 isformed between the leaf valve 51 and the float valve 55 such that it maydefine an amount of a lift when the leaf valve 51 is deflected.

Accordingly, hydraulic operating fluid in the oil chamber A which ispressurized in an expansion stroke of operation of the piston isintroduced to the leaf valve mechanism 50 by way of the passage 47 anddeflects the leaf valve 51 of the leaf valve mechanism 50 in accordancewith a difference in pressure between the oil chambers A and B to spacethe leaf valve 51 away from the valve seat face 61 so that it passesbetween the leaf valve 51 and the valve seat face 61 and flows into theoil chamber B.

In this instance, the amount of a lift of the leaf valve 51 is equal tothe difference in thickness between the spacer 53 and the float valve55, that is, equal to the gap d.

Since such spacer 53 and float valve 55 can be selected in suitablecombination from various general purpose spacers and leaf valves alreadyin use, the width of selection of such lift amount is very great, andvery fine selection is available.

Further, since the leaf valve 51 is not secured at an inner peripheralportion thereof, it has a comparatively low spring constant and hence ishigh in deflection and low in occurrence of local distorting force.

On the other hand, as one can clearly see from FIG. 8-10, when thehydraulic shock absorber is making an expanding movement and the pistonspeed is in the medium or high speed range, hydraulic operating fluid inoil chamber A in the cylinder 1 deflects the outer peripheral portion ofthe leaf valve 51 for the low speed range, which then deflects an outerperipheral portion of the leaf valve 54 so that it flows into oilchamber B and another predetermined attenuating force is generated. Theleaf valve 51 deflects downstream and contacts the leaf valve 54. Theleaf valve 54 the acts as a valve spring by applying a stronger forceagainst the leaf valve 51 so that the type of attenuation force changesfor medium and high speed.

Referring now to FIG. 9, there is shown a modification to the leaf valvemechanism shown in FIG. 8. While the leaf valve mechanism of FIG. 8 isconstructed such that the valve seat face 61 and the inner peripheralseat face 52 are formed in planes spaced from each other by a distanceequal to the thickness of the leaf valve 51, in the modified leaf valvemechanism shown in FIG. 9, such two seat faces 61 and 52 are formed inthe same plate while a spacer 56 having a thickness equal to thethickness of the leaf valve 51 is interposed between an inner peripheralseat face 52 and a spacer 53. In the present arrangement, the valve seatfaces can be worked readily.

Also with the modified leaf valve mechanism, characteristics of thehydraulic shock absorber in the very low speed range resulting fromselection of the gap d, that is, from determination of an amount of alift are similar to those of the leaf valve mechanism of FIG. 8.

Then, if selection of the gap d can be achieved appropriately with thespacer 53, then the float valve 55 may be omitted as in a furthermodified leaf valve mechanism shown in FIG. 10.

With the hydraulic shock absorber described above, since the leaf valvefor the generation of an attenuating force in the very low speed rangeof the piston speed and the leaf valve for the generation of anattenuating force in the medium or high speed range of the piston speedare set separately from each other, there is an advantage that controlsof attenuating force for different speeds of the piston can be madeindependently of each other.

Also, with the hydraulic shock absorber, the leaf valve for the very lowspeed range of the piston speed is not deflected excessively when theleaf valve for the medium or high speed range of the piston speed makesa deflecting movement, and accordingly, no excessive load is applied tothe leaf valve for the very low speed range and a possible trouble suchas a break of the leaf valve for the very low speed range is prevented.Accordingly, there is another advantage that the durability of the leafvalve for the very low speed range against deflection is improvedsignificantly and the life of such leaf valve is increased.

Further, where the attenuating valve is of the type wherein the two leafvalves for the low speed range and the medium of high speed range havingequal diametrical dimensions are disposed to act upon a common valveseat face, the valve device itself can be reduced in size compared witha valve device which includes two seat faces located in planes spacedfrom each other, and the degree of freedom in designing the leaf valveparticularly for the low speed range is wide. Consequently, the valvedevice can be applied even to a shock absorber having a small diameter.Further, since the leaf valve for the low speed range is disposed in anon-restricted condition due to contact thereof with the valve stopper,the spring constant of the leaf valve for the low speed range itself canbe decreased, which increases the width of selection of valves andincreases the degree of freedom in setting of attenuating force.Besides, since the stress of the leaf valve for the low speed range upondeflection is low and the local deflection is little, the leaf valve forthe low speed range is superior in durability.

What is claimed is:
 1. A hydraulic shock absorber, comprising:acylinder; a wall member defining a first hydraulic fluid chamber and asecond hydraulic fluid chamber; a hydraulic fluid port defined by saidwall member providing communication between said first hydraulic fluidchamber and said second hydraulic fluid chamber; a valve stopperpositioned on an end of said port, said valve stopper extendingpartially across said end of said port; high speed valve means forrestricting fluid flow from said first hydraulic fluid chamber to saidsecond hydraulic fluid chamber below a force corresponding to a mediumor high speed hydraulic fluid flow range and attenuating fluid flow insaid medium or high speed range, including plural leaf springs fixedlyattached at one end to said wall and cooperating with a valve seat todefine a gap and to control high speed fluid flow between said firsthydraulic fluid chamber and said second hydraulic fluid chamber; lowspeed valve means including a low speed leaf valve positioned in saidgap and acting against said valve seat to prevent fluid communicationbetween said first hydraulic fluid chamber and said second hydraulicfluid chamber through said port and for moving in said gap, away fromsaid valve seat under force corresponding to hydraulic fluid flow in alow speed range, said low speed leaf valve having a downstream innerperipheral surface abutting an upper surface of said valve stopper, andsaid downstream inner peripheral surface being partially moveable awayfrom said valve stopper in response to fluid flow between said first andsecond chambers, said valve stopper being supported between said highspeed valve means and said wall member, a thickness of said valvestopper spacing said low speed leaf valve from said plurality of leafvalves of said high speed leaf means to adjust damping characteristicsof the shock absorber.
 2. A shock absorber according to claim 1,wherein:a float valve is positioned within said gap, floatinglyconnected to said wall member for movement between said high speed valvemeans and said low speed leaf valve, said float valve having a thicknesswhich is smaller than said thickness of said valve stopper.
 3. A shockabsorber, according to claim 1, wherein:said wall member has an innerperipheral end face formed in a common plane with said valve seat.
 4. Ashock absorber, according to claim 3, wherein:a spacer is providedbetween said valve stopper and said wall inner peripheral end face.
 5. Ashock absorber, comprising:a cylinder; a piston positioned in saidcylinder and defining a first chamber on a first side of said piston,and a second chamber on a second side of said piston, said pistondefining a port providing communication from said first chamber intosaid second chamber; a valve seat around a first side of an end of saidport, said end of said port being adjacent said second chamber; a valvestopper positioned on a second side of said end of said port, said valvestopper being positioned downstream of said valve seat and extendingpartially across said end of said port; a low speed leaf valve includingan upstream outer peripheral surface and a downstream inner peripheralsurface, said upstream outer peripheral surface abutting said valve seatand said downstream inner peripheral surface abutting said valvestopper, said upstream outer peripheral surface being movable away fromsaid valve seat in response to fluid flow between said first and secondchambers, said downstream inner peripheral surface being partiallymovable away from said valve stopper in response to fluid flow betweensaid first and second chambers; a high speed leaf valve including aninner peripheral portion fixedly attached to said second side of saidend of said port at a position downstream of said valve stopper, saidhigh speed leaf valve extending across and downstream of said end ofsaid port and being positioned spaced from said low speed leaf valve,said high speed leaf valve flexing away from said valve seat in responseto flexing of said low speed leaf valve away from said valve seat.
 6. Ashock absorber in accordance with claim 5, wherein:said high speed leafvalve flexes away from said valve seat in response to flexing of saidlow speed leaf valve away from said valve seat beyond a predeterminedvalue.
 7. A shock absorber in accordance with claim 6, wherein:saidpredetermined value is dependent on a distance said high speed leafvalve is spaced from said low speed leaf valve.
 8. A shock absorber inaccordance with claim 6, wherein:a float valve is positioned betweensaid low speed vane and said high speed valve; said predetermined valueis dependent on a distance said high speed leaf valve is spaced fromsaid low speed leaf valve and a thickness of said float valve.
 9. Ashock absorber in accordance with claim 5, wherein:said high speed valveis a leaf spring valve which applies a leaf spring force to said lowspeed valve when said low speed leaf valve flexes away from said valveseat beyond a predetermined value.
 10. A shock absorber in accordancewith claim 5, wherein:said high speed leaf valve including an outerperipheral portion cooperating with said valve seat to control highspeed fluid flow between said first and second chambers.